Dockboard



NOV. 4, 1969 J. A MERR|CK IETAL 3,475,778

DOCKBOARD 4 Sheets-Sheet 1 Filed May 29, 1967 IA-VVEXTORS v1 E RRICKFIG-4 PATENT AGENTS Now-M4, 1969 v 4.1. A. MERRICK ETAL 3,475,778

DOCKBOARD 4 sheets-shed 2 Filed May 2Q. 1967 w M T @K ,l. S Xw T E Nwml# E ME G MP 4c, A AM .M E mm OD m JAA/V m FIGQ Nov. 4, 1969 y .1,A.MERRICK ETAL 3,475,778

DOCKBOARD Filed May 29, 1967 4 Sheets-Sheet 5 I.\-\7E \TUR. JOHN A.MERRICK ADRIAN P. HO\/ESTAD` PATENT AGENTS Nov. 4, 1969 J. A MERR|CKETAL 3,475,778

DOCKBOARD 4 Sheets-Sheet Filed May 29. 19e? FIGJO PATENT AGENTS D m m0K5 M .7C Amm WRHU v E. IMD.. if AN NMM Hm @A5 Y B United States PatentC) DOCKBOARD .lohn A. Merrick, Dundas, Ontario, and Adrian P. Hovestad,Burlington, Ontario, Canada, assignors to Service Steel & EngineeringLimited, Hamilton, Ontario, Canada Filed May 29, 1967, Ser. No. 642,089Int. Cl. B65g 11/14 U.S. Cl. 14-71 32 Claims ABSTRACT OF THE DISCLOSUREA new dockboard has a ramp assembly comprising a main plate pivoted tothe dockboard frame, and a lip plate at the front of the main plate;means for automatically extending the lip plate comprise a latchabletelescoping assembly disposed beneath the main plate, the telescopingassembly changing length as the main plate moves about its pivot, andthe latch being operative during pivoting movement of the main plate inone direction to prevent telescoping of the assembly, so that itoperates to extend the lip plate.

Field of the invention The invention is concerned with dockboards of thekind wherein a ramp assembly comprises a main plate pivoted to framemeans and a lip plate disposed at the front edge of the main plate, andmeans are provided for automatically extending the lip plate from astored inoperative position to an extended operative position in whichit forms an extension of the main plate.

Description of the prior art A number of such dockboards have beenproposed hitherto, and as specific examples may be mentioned U.S. patentspecification Nos. 3,137,017; 3,203,002 and 3,249,- 95 6. In thedockboard constructions described therein the lip plate is pivoted tothe main plate, and a flexible connection is provided between thedockboard frame and the pivoted lip plate; the main plate is movedupward and at a predetermined point of its upward movement the flexibleconnection becomes taut and further movement of the main plate isaccompanied by elevating pivoting movement of the lip plate.

Summary of the invention It is the principal object of the invention toprovide a dockboard of the kind specified and comprising a new mechanismfor automatically extending the lip plate.

It is another object to provide a dockboard of the kind specied andcomprising a new mechanism for restoring the ramp assembly automaticallyto its stored condition when required.

In accordance with the present invention there is provided a newdockboard comprising frame means, a main plate having a front edge,means pivotally connecting the main plate with the said frame means forpivoting movement about a respective rst pivot axis, a lip plate, meansmounting the lip plate at the main plate front edge for movementrelative to the main plate between a stored position and an operativeextended position, and lip-extending means operative to move the lipplate from its stored position to its operative position upon movementof the main plate about said rst pivot axis, said lipextending meanscomprising, telescoping means connected to the said frame means at apoint spaced from said first pivot axis and to the lip plate so thatmovement of the main plate about the rst pivot axis attempts to changethe length of the said telescoping means, and a rst latch meansoperative over a predetermined range of movement of the main plate tolatch the said telescoping means against change of length and therebycause the telescoping means to move the lip plate to its extendedposition.

In a particular preferred embodiment the lip plate rear edge is pivotedto the main plate front edge, so that the" lip plate pivots about arespective second pivot axis relative to the main plate between the saidstored and extended positions.

Also in accordance with the invention there is provided a new dockboardcomprising frame means, a main plate having a front edge, meanspivotally connecting the main plate with the said frame means forpivoting movement about a respective lirst pivot axis, a lip plate,means mounting the lip plate at the main plate front edge for movementrelative to the main plate between a stored position and an operativeextended position, lip-extending means operative to move the lip platefrom its stored position to its operative position upon movement of themain plate about the said lirst pivot axis, an arm connected with thesaid lip plate and movable thereby, and a reaction member on the framemeans disposed for cooperating engagement with the said arm, wherebymovement of the lip plate to return to its stored position causesengagement of the arm and the reaction member and the consequentapplication to the lip plate and thereby to the main plate of avertically-upwardly-directed force that moves the main plate above itsstored position, so that the main plate can thereafter descend undergravity to its stored position with the lip plate in its respectivestored position.

Description of the drawings FIGURE 1 is a general perspective viewshowing the dockboard ramp assembly in its stored position,

FIGURE 2 is a view similar to FIGURE 1 and showing the ramp assembly ina typical operative position,

FIGURE 3 is a plane section taken on the line 3 3 of FIGURE 1 to showthe spring-counterbalance and manual lever-handling arrangements,

FIGURE 4 is a plane section taken on the line 4-4 of FIGURE 1 to showthe arrangement of the lip-extending mechanism with the ramp assembly inthe said stored position,

FIGURE 5 is a perspective view to an enlarged scale of a detail of thesaid lip-extending mechanism,

FIGURE 6 is a view similar to FIGURE 4 with the ramp assembly in a rstlatch latching position and the mechanism set to raise the lip plate,

FIGURE 7 is a View similar to FIGURES 4 and 6 illustrating the raisingof the lip plate by the mechanism as the ramp assembly descends from theposition of FIG. 6,

FIGURE 8 illustrates the operation of the ymechanism to restore the lipplate to its dependent position and the ramp assembly to its storedposition when the latter descends below a predetermined second latchunlatching position,

FIGURE 9 shows a lower storage position to which the ramp assembly canbe put when required,

FIGURE 10 illustrates the operation of a safety latch feature in theevent that a transport backs against the lip plate while in the latchedextended position,

FIGURE 11 is a perspective view from below and to an enlarged scale of adetail of the latch arrangement of the lip-extending mechanism, and

FIGURE 12 is a cross-sectional view of part of another embodimentwherein the lip plate slides relative to the main plate between thestored and extended positions.

Like parts are given the same reference number in all figures of thedrawings, and parts are omitted from some of the figures to increase theclarity of illustration, when such parts are not employed in thefunction illustrated by that ligure.

Description of the preferred embodiments The particular form ofdockboard shown herein is adapted to be mounted as an integral unit intoa recess in a loading dock or platform so that, with the ramp assemblyin -the position shown in FIGURES 1 and 3 (called herein its storedposition), the main plate 16 thereof is approximately level with the topsurface of the dock, and the lip plate 17 is folded down to belapproximately flush with the front face of the dock. It will beunderstood that the term stored position is used for convenience andunder some conditions the dockboard will be operative for loading andunloading while in the so-called stored position. The invention also isapplicable to other forms of dockboard, such as a free-standing unitwithout a surrounding dock, and a unit of the type especially adaptedfor use with a stepdown dock. The term frame means is used herein forconvenience in terminology, and in the embodiment illustrated comprisesa box-like frame assembly; in other embodiments the frame means mayinstead comprise, for example, only the means by which the ramp assemblyand its associated mechanism are fastened to a suitable supportingstructure, which may be the dock, in which case the said supportingstructure operatively connects the fastening means together.

This particular dockboard comprises a frame assembly 18 of welded sheetmetal, made sufiiciently rigid for transport, installation andsubsequent use in known manner, as by suitable strengthening edges andcross bracing members such as 19; with this embodiment the frameassembly when installed is supported by the surrounding concrete of thedock 15. The main plate 16 has its rear edge hinged to the frameassembly by a pivot 20, the axis of the pivot being horizontal. The lipplate is hinged to the front edge of the main plate by a pivot 21 havingits axis parallel to that of the pivot 20. Referring especially toFIGURES 1, 3 and 4, in the stored position illustrated the main plate ishorizontal and the lip plate is generally vertical, in what is calledherein its dependent position, with its front edge engaged behind a pairof spaced stops 22.

Spring means 'comprising one or more heavy helical compression springs23 are connected between a member 24 fixed to the frame 18 and a bracket25 fixed to the underside of the main plate. Two extreme positions ofthis particular ramp assembly (called herein its first latch latchingand second latch unlatching positions) are shown respectively in FIGURES6 and 8, and it will be seen that as the springs 23 shorten and providemore spring force their upwardly-acting component is reduced; thearrangement of these spring means is made such that, in all positions ofthe ramp assembly whether the lip plate is in the said extended or inthe said dependent position, the effective Weight of the assembly justovercomes the bias of the spring means. With the lip plate in extendedposition, as shown in FIGURE 7, the effective Weight of the rampassembly acting against the spring means is increased, whereupon theassembly moves more positively downward.

The ramp assembly of this embodiment is moved by hand and to facilitateits handling a lever handle 26 is provided, the handle vbeing movablelongitudinally through a slot 27 in the main plate, from a storedposition shown in FIGURE 3 in broken lines to an operative positionshown in solid lines. In the stored position the lever is completelyconcealed beneath the main plate so that it does not obstruct thepassage of traffic. A ring 28 permits the operator to grasp the leverand also engages a bracket 29 to retain the lever in its lowermostposition.

The lip-extending mechanism comprises a telescoping arm assemblyconstituted by an outer, hollow, square 4 cross-section member 30pivoted at its rear end to th frame assembly by a pivot 31, the axis ofthe pivot being parallel to and spaced vertically from the axis of pivot20. An inner, hollow, square cross-section member 32 slides freelyinside the outer member 30, and another outer, hollow, squarecross-section member 33 slides freely over an extension 32a: (FIGURE 10)at the front end of the inner member 32. Referring especially to FIGURE10, a relatively stiff helical spring 34 is mounted in the enclosureformed between the extension 32a and the hollow member 33 and constantlyurges the member 33 in the forward direction. A bolt 35 passes freelythrough a 'cross piece 36 at the end of the inner member 32 and carriesat its other end a clevis 37, which is connected by a pivot 38 to adepending arm 39 rigid with the lip plate 17. The engagement of thecross piece 36 and the head of the bolt 35 limits the forward movementof the latter, while the compression of the spring 34 is adjusted bymeans of nuts 40.

A first gravity-operated latch member 41 is pivoted to the frame aboutthe same pivot 31 as the telescopic arm assembly and comprises anose-piece 42 (see especially FIGURE 5) that will pass through a slot 43in the outer member 30 to engage behind the rear end of the inner member32. An extension 44 of the member 41 extends to one side of the outermember 30, and in a predetermined lower range of movement of the rampassembly engages an upwardly-biased, latch-disengaging plunger 45mounted in a channel 46 fixed to the frame assembly, the plunger beingurged upwardly by a surrounding spring 47.

A second gravity-operated latch member comprises an arm 48 pivoted at 49to a bracket 50 that is in turn fastened to the inner member 32 andmovable therewith. A latch nose at the rear end of the arm 48 can engagea latch plate 52 fixed t0 shaft 53 which is pivotally mounted bybrackets 54 (FIGURE 11) to the underside of the main plate. The mountingof the plate 52 on its shaft is such that rearwardly-acting force on thearm 48 acts along a line passing through the pivot axis of the shaft,and there is no tendency for the shaft to rotate under the action ofthis force and release the latch. A downward extension 55 fixed to theshaft 53 is engageable in certain positions of the ramp assembly via ascrew 56 with a disengagement member 57 fixed to one side of the outermember 30, the screw permitting adjustment of the actual point ofengagement between itself and the member 57. A mechanism for restoringthe ramp assembly automatically to its stored condition comprises an arm58 which is pivoted at 59 to a depending portion of the bracket 50, andwhich has an extension 60 and a cam nose 61 that engage in predeterminedpositions of the ramp assembly with a reaction member 62 fastened to theframe means, in this embodiment fastened to the frame oor. The lowermostposition to which the arm 58 can fall under gravity about the pivot 59is set by a screw 63,

The operation of the lip-extending mechanism can now be described. Withthe dockboard in the stored position illustrated by FIGURES 1, 3 and 4both the said first and second latches are disengaged. The transport tobe loaded or unloaded, indicated generally herein by the reference 64,is backed up to the dock while the ramp assembly is in this position.The lever 26 is now moved to its operative position by an operatorstanding on the dock 15, and the ramp assembly is swung upward towardsthe position shown in FIGURE 6. The distances between the two pivots 20and 31 are fixed, but the distance between the two pivots 21 and 31increases as the ramp assembly moves upward, and the Vinner member 32slides within the outer member 30 (arrow 64) until at the elevated firstlatch latching position, with this embodiment the position illustratedby FIGURE 6, the first latch member 41 falls into place (arrow 65)behind the inner member rear end.

The operator now pushes the ramp assembly downward; the telescoping armassembly cannot decrease in length because of the irst latch, which isoperative between the frame and arm assemblies, and as the ramp assemblymoves downward (arrow 66, FIGURE 7) the lip plate is rotated upward(arrow 67). Another consequence of this downward movement is that thearm 48 of the second latch moves longitudinally forward relative to thelatch plate 52; at a second latch latching position illustrated byFIGURE 7, at which the ramp assembly is just above 'what is calledherein its upper operative po sition, and the lip plate is approximatelyat its point of greatest elevation relative to the main plate, the latchnose 51 slips down under gravity in front of the plate 52 (arrow 68) andthe second latch is now engaged. It is an important function of thespring 34 that if the second latch has not engaged by the time that thelip plate is at its maximum extension, the spring will compress underfurther downward movement of the main plate and shorten the telescopicarm the small amount required for this latching to take place; thespring thereby ensures the successful operation of the second latchwithout the need for extreme criticality in manufacturing and settingtolerances.

As shown in FIGURE 7, the plunger 45 has engaged the latch extension 44,but the spring 47 is too weak to disengage the first latch while it isstill under the load imposed by the ramp assembly. Any further downwardmovement of the ramp assembly can only take place by compressing thespring 34, and such compression takes place until the weight of the rampassembly that is not neutralized by the main spring means 23 is fullytaken up by the spring 34. The dockboard is now in a tioating conditionat which its weight is fully neutralized by springs; if at this pointthe ramp assembly is given even a slight upward jerk or push to what iscalled a iirst latch unlatching position, the telescoping arm assemblyelongates sufficiently to unload the iirst latch and allow the plunger45 to push the latch arm 41 out of engagement. In actual practice thisoating condition can only be achieved by moving the ramp very slowly,and at the usual speed of operation the additional downward force, dueto the kinetic energy of the assembly, always overloads the spring 34,which promptly bounces and lifts the ramp assembly a distance suiiicientto unload the iirst latch, the whole action taking place quickly andsmoothly. It should also be noted that the extent of possible downwardmovement of the plunger 45 is limited and after the plunger has movedits full extent it will stop and positively force the member 41 out ofengagement and unlatch the first latch.

The lip plate is now held extended by the second latch means, which areoperative between the main and lip plates, so that the lip plate willremain in the same attitude relative to the main plate during movementof the ramp assembly between what is called herein its upper operativeposition (approximately the position shown in solid lines in FIGURE 7)and its lower operative position (approximately the position shown insolid lines in FIGURE 8). The ramp assembly now moves gently down wardunder its own weight to the position shown in broken lines in FIGURE 7,in which the lip plate rests on the transport 64 to permit movement ofwares, etc. over the assembly between the truck and the dock. The bodyof a loaded transport will rise as it is unloaded, and vice versa, andthe ramp assembly can rise and fall with the transport body withoutchange of its attitude.

A particularly advantageous feature of our new dockboard is that it willreturn automatically to its stored position of FIGURE 4 upon thetransport driving away from the dock, even when the final operativeposition of the ramp assembly is below the stored position. Referringespecially to FIGURES 7 and 8, as the ramp assembly moves downward(arrow 69) the second latch member 55 moves rearward relative to theouter arm member 30,

and, at a second latch unlatching position shown in FIG- URE 8, which isjust below the above-mentioned lower operative position of the rampassembly, the engagement of the screw 56 and the plate 57 rotates theshaft 53 and disengages the second latch (arrow With the second latchdisengaged the main and lip plates can pivot freely relative to oneanother. At this time the extension 60 of the arm 58 is resting on theblock 62 with the nose 61 thereof in engagement with the front edge ofthe block.

The arm 58 and the members 32 to 39 together constitute what are calledherein propping means operative between the lip plate and the block 62,the effect of the propping means being to relieve the spring means 23 ofat least a substantial portion of the weight of the lip plate, to theextent that the spring means are able to lift the main plate as long asthe lip plate is propped in this manner. The action of the proppingmeans is therefore that, as soon as the second latch is released, aportion of the weight of the lip plate is relieved from the rampassembly and carried directly by the frame means via the propping means.The spring means 23 thereupon moves the main plate upward, moving thepivot 21 and the corresponding rear edge of the lip plate upward, theprop means remaining meanwhile in engagement with the block 62. Thepivot 59 and the associated end of the arm 58 move upward with theupward movement of the main plate, causing the extension 60 to pivotagainst the top face of the block 62 and lift the nose 61. Thearrangement is such that as the main plate reaches a position which isjust above the stored position (i.e. the position shown in broken linesin FIGURE 8) the nose is lifted clear of the block, whereupon thepropping means are no longer effective. The weight of the ramp assemblynow overcomes the spring means and the assembly moves downward, movingthe nose 61 over the top of the block so that the prop cannot obstructthe downward movement. As the main plate reached the said broken lineposition above the stored position the lip plate reached its fullydependent position with its lower edge just clear of the stops 22, andthe ramp assembly now settles gently to rest under its own weight, tothe position shown in FIG- URE 4 with the lip plate lower edge behindthe stops 22.

To show that it is a propping action which is obtained reference may bemade to the situation illustrated by FIG- URE 7, wherein the lip plateis resting on the transport 64, the transport constituting the proppingmeans. If at this time the second latch is manually disengaged the mainplate immediately lifts, dragging the forward edge of the lip platerearward over the transport oor until the edge clears the floor,whereupon `the lip plate drops directly to the stored position and theramp assembly drops directly downward.

Clearly such an operation cannot be obtained as a result of the rotationof the lip plate about its pivot, since there is no mechanism operativefor the transfer of force from the lip plate to the main plate.

Other valuable auxiliary features of our new dockboard will now bedescribed. One situation that arises frequently is that the transport isto be fully loaded, but the last wares cannot be placed in positionbecause of the presence of the lip plate; in this case we have providedmeans to enable the ramp assembly to be returned by the operator to thestored position, so that loading can be completed, witlliout the need tomove the transport away from the doc Referring especially to FIGURES 9and 1l, a key member 74 having two parallel arms 75 and 76 is mountedfor both longitudial and rotational movement in a bracket 77 fixed tothe underside of the main plate 16. This key member can be used tounlatch the second latch, and for this purpose the operator reachesthrough a slot 78 in the ramp plate, grasps the key member 74, lifts itvertically, and then rotates it anticlockwise (arrow 79) as seen inFIGURE 11, so that the arm is aligned with a rearward extension 80 onthe latch shaft 53; the key member is now pushed downward a distancesuicient to rotate the shaft 53 until the second latch is released. Theaction of the unlatched lip plate and the counterbalance spring means isto cause the main plate to lift and the lip plate to move back towardits stored dependent position, its front edge sliding on the transportfloor; when the lip plate leaves the transport floor it immediatelyfalls to its fully dependent position and the whole ramp assembly thenmoves downward, either under its own weight or with the assistance ofthe operator if required, until it has reached the stored position ofFIGURE 4.

It may be found at this time, or under other circumstances of operation,that the transport is below the iiush stored position, making loading orunloading difficult or impossible, and we have therefore made provisionfor the ramp assembly to be moved to a lower stored position shown inFIGURE 9. With the lip plate in dependent position the operator liftsthe ramp assembly using the lever arm 26, and then pulls upward on thekey member 74 to engage a stop 76a on the arm 76 with a correspondingprojection 58a of the arm 58. The operator lifts both the assembly andthe key member until a latch member 81 on the arm 58 engages in front ofa cooperating latch member S2 on the outer arm member 30. Thetelescoping arm assembly is now latched against change of length, and asthe assembly is lowered the lip plate is elevated a suflicient amountfor its lower edge to clear the upper stops 22. Thereafter the key 74 ispushed downward until the latch members 81 and 82 are disengaged by theaction of a stop 76]; on the arm 76; the lip plate now pivots toward thedock and can be engaged with the lower stop 22a, as seen in FIGURE 9.

Another possibility for which provision has been made is the case when atransport moves backward heavily against the dockboard While the lip isextended and latched. An impact involving a very small movement of thelip can be accommodated by compression of the spring 34 (FIG. l0), butthis spring is stiff and its range of movement is relatively small, andany greater impact could easily seriously damage the lip and perhaps thewhole dockboard.

Referring especially to FIGURE l0, a safety mechanism to guard againstthis possibility employs a third safety latch, comprising an arm 8-3pivoted at 84 to an assembly 85 carried on the member 33. A latch nose86 at the rear end of the arm 83 is arranged to engage a latch plate 87on the rod 53 just before the second latch becomes engaged. Any rearwardmovement of the transport 64 (arrow 88) causes corresponding movement ofthe member 33, assembly 8S and arm 83 (arrow 89); the

point of engagement of nose 86 and plate 87 is above the axis of shaft53, and such movement of the arm 83 will rotate the shaft to release thesec-ond latch and allow the lip plate to pivot, without damage to itselfor to the remainder of the dockboard.

Referring especially now to FIGURE 12, in the specific embodimentdescribed above the lip plate 17 is pivoted to the main plate 16 and isdependent therefrom in its Stored position. The invention also isapplicable to a dockboard having a ramp assembly of the type illustratedby FIGURE 12, wherein the lip plate is moved by the telescoping armassembly from an extended position shown in solid lines to a storedposition shown in broken lines and in which it is accommodated beneaththe main plate, the lip plate being mounted by guides 88 for slidingmovement between the two positions.

In the embodiments particularly described and illustrated the rampassembly is moved manually, and spring means 23 are employed to opposeits weight and make it capable of operation by a single operator ofaverage strength. The invention also is applicable to a dockboard inwhich the assembly is counterbalanced by a weight and/or the movement ofthe assembly is by means of a motor, such as a hydraulic or pneumaticpiston and cylinder. In a motorised embodiment the motor may be operatedto raise the assembly to the position of FIGURE 6 and then shut off,whereupon the assembly will move `downwards under its own weight,elevating the lip plate at the same time; it will usually be desirableto arrange that the motor also controls the downward movement so thatthe assembly can be lowered gently to the required position.

It will also be apparent to those skilled in the art that variousmodifications are possible to the apparatus as particularly described,within the scope of the invention. For example, in these embodiments thetelescoping means are operative to extend the lip plate as the mainplate descends, but it is also possible for them to extend the lip asthe main plate is raised, by simple reversal of the direction of actionof the connection between the telescoping arm means and the lip plate.In other embodiments the upward movement of the main plate causes thetelescoping arm means to decrease in length instead of increase, and thefirst latch means then are operative to prevent an increase in thelength of the telescoping arm means, as they are operative to extend thelip upon upward or downward movement of the main plate about its pivotaxis.

What we claim is:

1, A dockboard comprising frame means, a main plate having a front edge,means pivotally connecting the ramp plate with the said frame means forpivoting movement about a respective first pivot axis, a lip plate,means pivotally mounting the lip plate at the main plate front edgeabout a second pivot axis for movement relative to the main platebetween a stored position and an operative extended position, andlip-extending means operative to move the lip plate from its stored toits operative position upon movement of the main plate about said firstpivot axis, said lip-extending means comprising telescoping meansconnected to the said frame means at a point spaced from said firstpivot axis and to the lip plate so that movement of the main plate aboutthe first pivot axis attempts to change the length of the saidtelescoping means, a first latch means operatively connected between theframe means and said arm means and operative over a predetermined rangeof movement of the main plate to latch the said telescoping meansagainst change of length and thereby cause the telescoping means to movethe lip plate to its extended position, and second latch meansoperatively connected between the main plate and the lip plate andlatched by the action of the said telescoping means when the lip platehas been moved thereby to the said extended position to latch the lipplate in the extended position.

2. A dockboard as claimed in claim 1, wherein the said telescoping meansincrease in length as the main plate is raised, and are latched by thefirst latch means against decrease in length as the main plate movesdownward from an uppermost position, so that downward movement of themain plate from the said uppermost position to an upper operativeposition is accompanied by extension of the lip plate.

3. A dockboard as claimed in claim 1, wherein the said telescoping meanscomprise first and second members disposed in telescoping relation toone another and operatively connected between the frame means and thelip plate, a third member disposed in telescoping relation to one of thefirst and second members, and spring means operative in the direction oftelescoping movement of the telescoping means between the third memberand its associated member.

4. A dockboard as claimed in claim 2, wherein the said telescoping meanscomprise a first member pivoted to the said frame means about arespective third pivot axis spaced from the first pivot axis, a secondmember in telescoping relation to the first member and latchable by thefirst latch means to prevent movement thereof toward the said thirdpivot axis and thereby prevent decrease in length of the telescopingmeans, the said second latch means comprising a latch arm carried by thesecond member, and a cooperating latch member carried by the main plate.

5. A dockboard as claimed in claim 4, wherein the said second latchmeans carried by the main plate comprise a rotatable latch memberengaged by the said second latch means arm along a line passing throughthe axis of rotation of the rotatable member.

6. A dockboard as claimed in claim 5, wherein means for unlatching thesecond latch means upon movement of the ramp plate below a predeterminedposition comprises disengagement means movable with the said firsttelescoping member and operatively engageable with the said latchrotatable member to rotate the latter and thereby unlatch the latch.

7. A dockboard as claimed in claim 1 and comprising a safety latch meansconnected to and movable with the lip plate, and operative under theaction of a force upon the lip plate in the general plane of the rampassembly and of greater than predetermined magnitude to unlatch thesecond latch means and thereby permit the lip plate to pivot relative tothe main plate.

8. A dockboard as claimed in claim 5, wherein the said rotatable latchmember of the second latch is engaged by safety latch means connected toand movable with the lip plate, and operative under the action of aforce upon the lip plate in the general plane of the lip assembly and ofgreater than predetermined magnitude, the safety latch means engagingsaid rotatable latch member along a line displaced from the said axis ofrotation, so that the said movement of the safety latch means with thesecond telescoping member rotates the rotatable latch member and therebyunlatches the second latch means.

9. A dockboard as claimed in claim l, wherein means for unlatching thefirst latch means comprise a spring loaded plunger engageable with thefirst latch over a predetermined lower range of movement of the mainplate, and the said telescoping means includes spring means compressiblein the direction of telescoping motion of the telescoping means by theload of the ramp assembly, the load of the assembly upon the first latchholding it in engagement against the action of the said plunger, and thesaid spring means permitting unloading of the first latch whereupon theplunger can unlatch the said first latch.

10. A dockboard as claimed in claim 1, and comprising spring meansoperably connected between the frame means and the ramp assembly andurging the assembly for upward movement, said spring means normallybeing unable to move the ramp assembly upward against the weight thereofacting downward under gravity, prop means operably engageable betweenthe lip plate and the frame means upon movement of the main plate belowa lower operating position, said prop means in said operative engagementrelieving the spring means of at least part of the weight of the rampassembly such that the spring means moves the ramp assembly upward aboveits said stored position, and prop disengaging means disengaging theprop means from between the lip plate and the frame means upon movementof the ramp assembly above the stored position, so that the rampassembly thereafter descends under gravity to its stored position.

11. A dockboard as claimed in claim 10, and comprising fourth latchmeans carried by the said telescoping means, cooperating fourth latchmeans on the said prop means, means operable by an operator for manuallyengaging the said fourth latch means upon upward movement of the rampassembly and thereby latching the telescoping means against change inlength, whereby downward movement of the ramp assembly with the fourthlatch means latched so extends the lip as to permit the assembly to bemoved to a lower stored position.

12. A dock-board as claimed in claim 1, wherein the telescoping meanscomprise, a first telescoping member pivoted to the frame means, a firstlatch member pivoted to the frame means, a second telescoping memberpivotally connected with the lip plate and telescoping with respect tothe rst member, the second member being engageable with the said firstlatch member to constitute rst latch means, a second latch membercarried by the second telescoping member, another second latch membermounted on the underside of the main plate and engageable with the firstmentioned second latch member to constitute said second latch means, thefirst latch being latched upon upward movement of the ramp assemblyabove a first latch latching position and the second latch being latchedupon downward movement of the ramp assembly to a second latch latchingposition above an upper operative position of the ramp assembly, meansfor unlatching the first latch means upon movement of the ramp assemblyto a first latch unlatching position below the said second latchlatching position, and means for unlatching the second latch means uponmovement of the ramp assembly to a second latch unlatching positionbelow a lower operative position of the assembly.

13. A dockboard as claimed in claim 12, and comprising means formanually unlatching the said second latch means while the ramp assemblyis between the said second latch latching and unlatching positions.

14. A dockboard as claimed in claim 12, and comprising a thirdtelescoping member in telescoping relation with the said second memberand pivotally connecting the telescoping means to the lip plate, and aspring interposed between the second and third telescoping members andoperative in the direction of telescoping motion of the telescopingmeans.

15. A dockboard comprising frame means, a main plate having a frontedge, means pivotally connecting the ramp plate with the said framemeans for pivoting movement about a respective first pivot axis, a lipplate, means mounting the lip plate at the main plate front edge formovement relative to the main plate between a stored position and anoperative extended position, and lip-extending means operative to movethe lip plate from its stored to its operative position upon movement ofthe main plate about the said first pivot axis, said lip-extending meanscomprising arm means operatively engageable with the frame means and thelip plate, first latch means operable over a predetermined range ofmovement of the main plate to latch the arm means to the frame means forthe arm means to move the lip plate to the operative position upon thesaid movement of the main plate over the predetermined range, firstlatch unlatching means operably engageable with the first latch meansover another predetermined range of movement of the main plate to urgesaid latch means to unlatched condition, said unlatching means beinginoperative while the first latch means is loaded by the ramp assemblyand being operative upon unloading of the first latch means.

16. A dockboard as claimed in claim 15, wherein said unlatching meansare operative upon movement of the main plate beyond the said anotherpredetermined range of movement to engage the first latch meanspositively and unlatch the first latch means while loaded by the rampassembly.

17. A dockboard as claimed in claim 15, wherein the said lip-extendingarm means comprises spring means interposed between the lip plate andthe first latch means for unloading the ramp assembly from the firstlatch means by spring action of the spring means during movenent of theramp assembly and subsequent reaction thereo 18. A dockboard as claimedin claim 15, wherein the lip plate has front and rear edges, the lipplate rear edge is pivoted to the main plate front edge so that the lipplate pivots about a respective second pivot axis relative to the mainplate between the said stored and extended positions, and the saidlip-extending arm means are latched by the first latch means to theframe means as the main plate moves downward from an uppermost position,so that downward movement of the main plate is accompanied by extensionof the lip plate.

19. A dockboard as claimed in claim 15, wherein said iirst latch meanscomprise a latch member mounted bythe frame means, and wherein saidunlatching means comprises a spring urged plunger mounted by the framemeans for operative engagement with the said latch means, and urging thelatch member to unlatch the latch means.

20. A dockboard as claimed in claim 17, comprising second latch meanshaving relatively movable latch members and operatively connected by thelip-extending arm means between the main plate and the lip plate tolatch the lip plate in the said extended position when it has been movedto that position, and wherein the said spring means is also interposedbetween the lip plate and the second latch means and permits relativemovement of the second latch means latch members for latching thereofafter the lip plate has moved to the said extended position.

21. A dockboard comprising frame means, a main plate having a frontedge, means pivotally connecting the ramp plate with the said framemeans for pivoting movement about a respective rst pivot axis, a lipplate, means mounting the lip plate at the main plate front edge formovement relative to the main plate between a stored position and anoperative extended position, and lip-extending means operative to movethe lip plate from its stored to its operative position upon movement ofthe main plate about the said lirst pivot axis, said lip-extending meanscomprising arm means operatively engageable with the frame means and thelip plate, rst latch means operable over a predetermined range ofmovement of the main plate to latch the arm means to the frame means andcause the arm means to move the lip plate to the operative position uponthe movement of the main plate over the said predetermined rangethereof, second latch means having relatively movable latch members andoperatively connected by the arm means between the main plate and thelip plate to latch the lip plate in the said extended position when ithas been moved to that position, and said arm means comprising springmeans interposed between the lip plate and the second latch means andpermitting relative movement of the second latch means latch members forlatching thereof after the lip plate has moved to the said extendedposition.

22. A dockboard as claimed in claim 21, wherein the lip plate has frontand rear edges, the lip plate rear edge is pivoted to the main platefront edge so that the lip plate pivots about a respective second pivotaxis relative to the main plate between the said stored and extendedpositions, and the said lip-extending arm means are latched by the rstlatch means to the frame means as the main plate moves downward from anuppermost position, so that downward movement of the main plate isaccompanied by extension of the lip plate.

23. A dockboard comprising frame means, a main plate having a frontedge, means pivotally connecting the ramp plate with the said framemeans for pivoting movement about a respective lirst pivot axis, a lipplate, means mounting the lip plate at the main plate front edge formovement relative to the main plate between a stored position and anoperative extended position, and lip-extending means operative to movethe lip plate from its stored to its operative position upon movement ofthe main plate about the said first pivot axis, spring means operativelyconnected between the frame means and the ramp assembly and urging theassembly for upward movement, said spring means normally being unable tomove the ramp assembly upwards against the weight thereof actingdownward under gravity, and prop means operably engageable between thelip plate and the frame means upon movement of the main plate below alower operating position, said prop means in said operative engagementrelieving the spring means of at least part of the weight of the rampassembly such that the spring means moves the ramp assembly upward aboveits said stored position.

24. A dockboard as claimed in claim 23, and comprising prop disengagingmeans disengaging the prop means from between the lip plate and theframe means upon movement of the ramp assembly above the storedposition, so that the ramp assembly thereafter descends under gravity toits stored position.

25. A dockboard as claimed in claim 24, and comprising second latchmeans operatively connected between the main plate and the latch plateand latched by the action of the lip extending arm means when the lipplate has been moved thereby to the said extended position to latch thelip plate in the extended position, and means for disengaging the saidsecond latch means upon movement of the ramp plate below the said loweroperating position.

26. A dockboard as claimed in claim 25, wherein the lip plate has frontand rear edges, the lip plate rear edge is pivoted to the main platefront edge so that the lip plate pivots about a respective second pivotaxis relative to the main plate between the said stored and extendedpositions, and the said lip-extending arm means are latched by the iirstlatch means to the frame means as the main plate moves downward from anuppermost position, so that downward movement of the main plate is:accompanied by extension of the lip plate.

27. A dockboard as claimed in claim 26, wherein the upward movement ofthe main plate is accompanied by movement of the lip plate toward itsstored position, the lip plate reaching the said stored position as themain plate reaches a position above the stored position, so that theramp assembly descends under gravity with the lip plate in the storedposition.

28. A dockboard as claimed in claim 26, wherein said prop means comprisea prop arm disposed beneath the ramp plate and operatively connected tothe lip plate, and said prop disengaging means comprise a prop latch onsaid prop arm operably engageable with the frame means, and latchdisengaging means on said prop arm operable to disengage the prop latchas the ramp assembly reaches the said position above the storedposition.

29. A dockboard as claimed in claim 26 wherein said prop means comprisethe said lip-extending arm means, a prop arm connected to thelip-extending arm means for operative connection to the lip plate, andsaid prop disengaging means comprise a prop latch on said prop armoperably engageable with the frame means, and latch disengaging means onsaid prop arm operable to disengage the prop latch as the ramp assembly'reaches the said position above the stored position.

30. A dockboard as claimed in claim Z9 wherein said prop arm ispivotally connected to the lip-extending arm means and said propdisengaging means comprise a stationary prop latch member on the framemeans, another latch member on the frame means, another latch member onthe prop arm, and a latch-disengaging extension on the prop arm spacedfrom the pivotal connection of the arm with the lip-extending arm means,the pivoting of the prop arm as the ramp assembly moves about the tirstplvot axis operatively engaging the extension and the frame means todisengage the prop arm latch member from the stationary latch memberwhen the ramp assembly moves above the stored position.

3 1. A dockboard comprising frame means, a main plate having a frontedge, means pivotally connecting the ramp plate with the said framemeans for pivoting movement about a respective iirst pivot axis, a lipplate, means mounting the lip plate at the main plate front edge formovement relative to the main plate between a stored position and anoperative extended position, lip-extending means operative to move thelip plate from its stored to its operative position upon movement of themain plate about the said irst pivot axis, said lip-extending meanscomprising arm means operatively engageable with the frame means and thelip plate, first latch means operable over a predetermined range ofmovement of the main plate to latch the arm means to the frame means andcause the arm means to move the lip plate to the operative position uponthe movement of the main plate over the said predetermined rangethereof, second latch means operatively connected by the lip-extendingarm means between the main plate and the lip plate to latch the lipplate in the said extended position when it has been moved to thatposition, and safety latch means connected to and movable with the lipplate, and operative under the action of a force upon the lip plate inthe general plane of the ramp assembly and of greater than predeterminedmagnitude to unlatch the second latch means and thereby permit the lipplate to pivot relative to the main plate.

32. A dockboard as claimed in claim 31, wherein the said second latchmeans comprise a latch arm carried by said lipextending arm means, arotatable latch member carried by the main plate and engaged by the saidsecond latch means arm along a line passing through the axis of rotationof the rotatable member, and wherein the said safety latch means engagesthe said rotatable latch member along a line displaced from the saidaxis of rotation, so that the said movement of the safety latch meanswith the lip plate rotates the rotatable latch member and there- 5 byunlatches the second latch means.

References Cited UNITED STATES PATENTS 10 3,327,335 6/1967 Beckwith14-71 3,137,017 6/1964 Pfleger 14-71 3,203,002 8/1965 McGuire 14-713,249,956 5/1966 Zajac 14-71 3,323,158 6/1967 Loomis 14-71 NILE C.BYERS, J R., Primary Examiner

